In general, a developing cartridge includes a photoconductor drum on which an electrostatic latent image is to be formed, a developer carrying member rotatable with and contacting the photoconductor drum to supply developer on the photoconductor drum, and a doctor blade configured to contact the developer carrying member and to regulate the thickness of the developer layer carried on the developer carrying member while the developer carrying member is rotating. In one known developing cartridge, a doctor blade is bent at an acute angle at its portion contacting the developer cattier; to be more specific, a distal end portion of the doctor blade is bent at an acute angle and extends in a direction away from the developer carrying member. The developer carried on the developer carrying member is charged when passing under the doctor blade, and the charged developer is then supplied to an exposed area of the photoconductor drum.
According to this conventional developing cartridge, if the thickness of the developer layer carried on the developer carrying member is thick, the developer layer is compressed at an interface between the developer carrying member and the photoconductor drum, and the compressed developer may disadvantageously flow into or be scattered over a non-exposed area of the surface of the photoconductor drum, with the result that printing failure such as fog occurs.
Further, the doctor blade is configured such that the bent portion thereof slidably contacts the developer carrying member at a contacting edge of the bent portion, and an angle between the plane tangent to the developer carrying member and passing through the contacting edge and the bent portion at the distal end of the doctor blade becomes an acute angle. Accordingly, foreign objects such as developer and paper powder would easily enter an interface between the developer carrying member and the doctor blade. If foreign objects enter the interface and they are compressed with the developer, the mixture (aggregate) of developer and the foreign objects adheres to the surface of the photoconductor drum, which leads to printing failure.
In view of the above, it would be desirable to provide a developing cartridge which can reduce the thickness of the developer layer carried on the developer carrying member and prevent foreign objects from adhering to the developer carrying member.